U形切槽梁同时测定准脆性材料的动静态拉伸强度和断裂韧度新方法研究

Two suggested test methods were proposed by International Society for Rock Mechanics (ISRM), however the following problems are existed, i.e. the load lines of both Brazilian disc ends cracking ahead of the disk center and non-pure tension loading on the diameter in tensile strength testing， and complex production of cracked chevron notched Brazilian disc specimens, crack tip in three-dimensional force, the impact of notch width and test results less than the others’ in fracture toughness testing. Neither dynamic tensile strength nor dynamic fracture toughness test methods was recommended by ISRM, and research on these aspects are in the ascendant. To solve the above bottleneck problems, the new method of concurrently measuring the static and dynamic tensile strength and fracture toughness for quasi-brittle materials using U-notched beams are brought forward. Firstly, based on the previous studies, concurrent measurement of tensile strength and mode Ⅰ fracture toughness of concrete with U-notched beams are proposed. Secondly, the new method of simultaneously measuring of tensile strength and mode Ⅱ fracture toughness of quasi-brittle materials with U-notched beams is explored, and the impact of tensile strength and mode Ⅱ fracture toughness on different dimensionless radii of the U-notched beams will be discussed, and the biggest dimensionless radius in a single parameter (mode Ⅱ fracture toughness) test method with U-notched beams and its error will also be studied. Thirdly, based on the static two-parameter test method, concurrent measurement of dynamic tensile strength and dynamic fracture toughness of quasi-brittle materials using U-notched beams are proposed. The research results will lay a sound theoretical and application foundation for promoting and applying the method of simultaneous measurement two static or dynamic parameters with U-notched beams.

国际岩石力学学会建议测试方法中，拉伸强度测试时巴西圆盘两加载端先于圆盘中心开裂、加载直径处于非纯拉伸；断裂韧度测试时人字形切槽巴西圆盘制作复杂、裂尖三维受力、切槽宽度影响、测试结果小于其他方法等；学会尚未提出岩石动态拉伸强度和断裂韧度的建议测试方法，该方面研究方兴未艾。为解决以上瓶颈问题，提出用U形切槽梁同时测定准脆性材料的动静态拉伸强度和断裂韧度的新方法。首先，在已有研究基础上，提出用U形切槽梁同时测定混凝土的拉伸强度和Ⅰ型断裂韧度。其次，探索U形切槽梁同时测定准脆性材料的拉伸强度和Ⅱ型断裂韧度，讨论拉伸强度和Ⅱ型断裂韧度对不同无量纲曲率半径U形切槽梁的影响，研究Ⅱ型断裂韧度U形切槽梁测试法所允许的最大无量纲曲率半径及误差。第三，基于静态双参数测试法，提出用U形切槽梁同时测定准脆性材料的动态拉伸强度和断裂韧度。研究成果将为推广和应用U形切槽梁动静态双参数测试法奠定坚实的理论与应用基础。

国际岩石力学学会ISRM建议测试方法中，拉伸强度测试时巴西圆盘两端加载线先于圆盘中心开裂、加载直径上非纯拉伸状态；断裂韧度测试时人字形切槽巴西圆盘试样制作复杂、裂尖三维受力、受切槽宽度影响、测试结果小于其他测试法。ISRM尚未提出岩石动态拉伸强度和断裂韧度的建议测试方法，该方面研究正方兴未艾。为解决以上瓶颈问题，提出用U形切槽梁同时测定准脆性材料的拉伸强度和断裂韧度的新方法。首先，提出了用U形切槽梁同时测定混凝土的拉伸强度和Ⅰ型断裂韧度，推广应用准脆性材料双参数测试法。其次，探索了U形切槽梁同时测定准脆性材料的拉伸强度和Ⅱ型断裂韧度的新方法，研究了高围压状态下岩石力学特性和本构模型研究。第三，基于静态双参数测试法，提出了测定准脆性材料的动态起裂韧度、扩展韧度及止裂韧度的新方法。